Wednesday, October 1, 2014

Fun With Broken Arrows

Have you ever lost something important at work? An expensive tool, a critical spreadsheet, or maybe an entire intern? You know that sinking feeling you get when you realize how badly you screwed up? Just imagine how much worse it would be, if that intern were made of plutonium.

The U.S. military classifies nuclear weapons incidents on a scale that starts small at “Dull Sword,” indicating an event which could have become a nuclear incident under different circumstances. For example, in 1950 the crew of a B-36 Peacemaker bomber that was experiencing engine trouble decided, before bailing out, to drop their Mark 4 nuclear bomb on Canada. Because fuck Canada, right? The bomb was only loaded with a practice nuclear core, however, which made a nuclear detonation impossible.

1950, in fact, witnessed a second Dull Sword event when a B-50 also experienced engine trouble and its crew also decided to drop their Mark 4 nuclear bomb on Canada. Yeah, by 1950 the United States Air Force had already dropped as many nuclear bombs on Canada as it had on Japan. And why the hell not? It’s nothing but snow, hockey, and socialized medicine up there. It’s practically Russia already.

Here you go, Canada. Have two of these on Uncle Sam.

Next in order of severity is a Bent Spear incident, which involves a relatively minor mistake or accident which has only the smallest probability of ending civilization. The most famous of these occurred in 2007 when a B-52 that was supposed to be ferrying unarmed cruise missiles for disposal was accidentally loaded with six live nuclear warheads, each one having a maximum yield of 150 kilotons. That’s a total explosive potential around 50 times larger than the “Little Boy” bomb that killed a hundred thousand people when dropped on Hiroshima. Breaking with tradition, these cruise missiles were not fired at Canada, but were instead delivered to Barksdale Air Force Base in Louisiana, where someone finally noticed they were live weapons. By then, a full two days had passed since they were improperly removed from their secure bunker. In that time, no one at the site of origin had noticed that six nuclear warheads were missing.

Next comes Empty Quiver, which is the theft, seizure, or other inadvertent loss of a nuclear weapon. Boooooring. Wake me up when we get to…

A Broken Arrow. These are the mack daddies of nuclear weapons incidents. A Broken Arrow is any incident in which there's a risk of detonation or release of fissile warhead material. Since the 1950’s, there have been approximately a gajillion of these incidents. Taken individually, most involved no or fairly low probabilities of accidental nuclear detonation, but put all of them together and it’s a fucking miracle that we haven’t accidentally vaporized a bunch of people.

The first Broken Arrow I’m aware of happened in 1950—a real banner year for nuclear mishaps—when a nuclear-armed B-29 crashed three minutes after takeoff. The nuclear core was aboard but not installed at the time of the crash, so the fissile plutonium merely cooked in the fire until they could put it out. No big.

Not to be outdone by the Americans, a Soviet submarine in 1977 accidentally dropped a nuclear missile into the northern Pacific Ocean. There was a build-up of pressure in the launch tube and they just, you know, accidentally dropped it overboard. Woops.

In fairness to the Soviets, the ocean floor is a popular place for accidentally leaving nuclear weapons. In 1965, the U.S. Navy dropped one off an aircraft carrier while steaming south of Japan. The bomb, the pilot, and the aircraft they were both attached to rolled off an elevator and were never recovered. The loss was not revealed, however, until 1981. Apparently, someone at the Pentagon feared that Japanese people might have strong opinions about nuclear weapons for some strange reason.

God, Japan, you’re such a Canada.

My absolute favorite broken arrow, however, has to be the 1961 crash of a B-52 in Goldsboro, North Carolina. The Air Force, having learned absolutely nothing from the shenanigans back in 1950, had armed the aircraft with two Mark 39 thermonuclear bombs—both live, with their plutonium cores fully installed. During a refueling operation off the coast, the tanker crew noticed a fuel leak on the B-52’s right wing. The pilots attempted to make an emergency landing, but the bomber began to break up at around 10,000 feet and the crew ejected, leaving the live bombs in their falling aircraft.

On one of the bombs, three of four safety mechanisms completely failed on the way down and the bomb armed itself for a ground burst. Following its programming to the letter, it deployed its drag chute to slow its descent, activated its detonation triggers, and charged its firing capacitors. When it hit the ground in a muddy field, the trigger mechanism activated, sending an electrical signal to the firing capacitors. If that signal had arrived, the capacitors would have discharged and the bomb would have detonated.

If it had gone off, according to calculations I made using Nukemap, the 3.8 megaton bomb would have created a crater five hundred feet deep. The fireball would have been a mile wide. It would have leveled every building for five miles in every direction. It would have inflicted third degree burns on 100% of exposed persons within twelve miles. The cloud of radioactive fallout would have stretched four hundred miles under moderate wind conditions, reaching as far as Atlanta or Philadelphia depending on wind speed and direction. Something like 20,000 people would have died.

Only an arm/safe switch—the single safety mechanism which worked properly on that bomb—stopped this from happening.

But, you protest, that arm/safe switch couldn’t possibly have malfunctioned, right? It’s surely failsafe, right? Right? RIGHT?! For fuck’s sake, Robyn, that last switch must have been very reliable!

Actually, now that you mention it, do you remember that there were two bombs? On the second bomb, the triggers did not activate, the capacitors did not charge, and the drag chute did not open. Many of its components were never found, but they did recover the arming switch—the same switch that, on the first bomb, was all that stood in the way of a nuclear detonation.